In many medical and laboratory applications, it is necessary to provide or administer a single-dose or an exactly measured dose of a liquid agent, such as medication, reagents, and control solutions for evaluating diagnostic systems. Particularly in laboratory applications and in certain medical applications involving diagnostic tests, reagents are required to be provided in very precise amounts in an assay process. For such purposes, certain agents and reagents are provided in containers or packages which hold only a single dose of liquid or which provide for the delivery of only a single dose from a multi-dose volume of liquid.
One such application in which precise amounts of reagent fluid are required is in the fabrication and patient use of systems for measuring analyte (such as glucose, cholesterol, and narcotics or the like) concentrations in a physiological fluid, such as blood, interstitial fluid, urine, and saliva. Such systems typically include test strips containing a reagent material to which a physiological sample is applied, and meters configured for receiving the test strips and determining the target analyte concentration of the sample on the test strip.
During the manufacturing and fabrication of the test strips, the strips are typically quality control checked by batch sampling methods in which a monitoring agent, often called a control solution, formulated to mimic blood is used to test the accuracy and efficacy of the test strips. Examples of such control solutions are disclosed in U.S. Pat. Nos. 5,187,100 and 5,605,837. The accuracy of test strip meters is also checked during the manufacturing process by using the meter with test strips known to meet quality control standards and having such a control solution applied to them.
Such quality control of test strips and meters is similarly performed directly by the patient or user of such meters and test strips as well as medical personnel treating such a patient. The patient or medical worker is supplied with a control solution, such as when receiving a meter or obtaining a new package of test strips, and is typically instructed to perform a quality control check upon the occurrence of any of the following events: opening a new package of test strips; using a new meter; when training or learning to use the meter and test strips; after the meter is dropped or the like; when the analyte measurement results do not reflect how the patient is currently feeling (e.g., when a glucose measurement result indicates a substantially high level of blood glucose level but the patient is feeling quite normal); or when a glucose measurement result is normal but the patient is feeling sick.
Control results that fall outside an expected range may indicate: user procedural error; a dirty meter or test strip container; test strip contamination, deterioration, damage or expiration; meter malfunction; control solution expiration; and/or a control solution which is outside of an acceptable temperature range, etc.
The above-described control solutions are typically packaged in a plastic container or a glass vial. FIG. 1 illustrates an example of a prior art container 1 with a removable cap 2 used for containing and dispensing a control solution The dispensing end of these containers is typically configured with a small opening at the end of a taper 3 through which a relatively imprecise droplet of control solution can be dispensed by squeezing the bottle.
With continued reference to FIG. 1, the container 1 holds a volume of liquid control solution, typically having a volume of about 3 to 5 ml, which provides about 100 to 200 dosages which typically lasts about three months. To apply the control solution, the cap 2 is removed and the container 1 is tilted so that that its dispensing portion 3 is held several millimeters over a test strip's reagent area. The user then applies a slight squeeze pressure to container to dispense a droplet of the control solution onto the reagent area.
Such containers and the steps for dispensing control solution from them have their drawbacks. For example, the container is repeatedly opened over an extended period of time, thereby repeatedly exposing the control solution to contaminants in the air and on surfaces, such as the user's fingers, which carry contaminants. In addition, because the users of such control solutions may often have poor dexterity (such as diabetics), a user may frequently fumble and/or drop the cap, which may further contaminate the solution. Such contamination can cause erroneous analyte test results. If it is determined that the control solution has become contaminated the entirety of the control solution must be thrown away, and a new container opened, which can become costly. Moreover, when this happens, a new container of control solution may not be readily available to the user, possibly leaving him or her in a medically risky situation.
Furthermore, such prior art control solution containers are problematic in that, because such a relatively large volume of the control solution is provided, the efficacy of the control solution may expire well before a majority of the control solution is used, which also adds to the cost of treating the patient. The shelf-life of the control solution sealed within its original containment is usually about one to two years, but once the user opens the solution container, the shelf-life quickly drops to only a few months due to the contamination problem mentioned above.
In addition, the user may forget to replace the cap on the container causing the control solution to evaporate thereby changing the analyte concentration which results in erroneous values. Additionally, it can be difficult to precisely and accurately dispense the requisite volume of the control solution from within such prior art containers. The volume dispensed is highly user dependent in that the user may apply too much control solution by over-squeezing the container or may apply too little solution by not squeezing enough.
There is yet another drawback of prior art control solution dispensers: while advancements are rapidly being made in the development of systems and devices for measuring analyte concentrations, there has been limited advancement in the area of control solution containment and dispensing for use with these advanced systems and devices.
In particular, advancements have been made in minimizing the pain experienced by the patient in obtaining a sample of blood or interstitial fluid as well as in minimizing the time and the number of steps necessary to carry out a glucose concentration measurement. The former has been accomplished by reducing both the sample volume size necessary to effect an accurate analyte measurement and the size of the needle for obtaining the sample fluid. The latter has been realized by the integration of various components used for the measurement process.
Specifically, microneedles are now being integrated with test strips. In these tester devices, the integrated needle/test strips include a capillary channel which extends from an opening in the distal tip of the microneedle to the sensor reagent area or matrix area within the test strip.
Additionally, in certain of these embodiments, the tester is partially dispensed from the meter in an automatic or semi-automatic manner for accessing and collecting the sample fluid, yet remains electrically or photometrically (as the case may be) in contact or engaged with the meter during such fluid access and collection, thereby obviating the need for the user to handle the test strip.
The microneedle configuration clearly saves time and reduces the risk if injury to the patient and contamination to the strip and meter. As such, in a single step, physiological fluid can be accessed (by penetrating the skin with the microneedle), transferring only the minimum amount of sample necessary to the sensor (by means of the capillary channel) and determining the target analyte concentration within the sample (by means of the engaged meter).
In order to evaluate the performance of such an integrated system, the meter is equipped with “on board” diagnostic electronics and software, and a control solution is provided for testing the efficacy of the test strip's sensor.
While the prior art control solution dispensers can be used in this case to evaluate the test strips by dispensing a droplet of control solution on to the designated sensor area of the test strip as mentioned above, there is no provision for evaluating the effectiveness of the integrated microneedle. One could deposit a droplet of control solution onto a sterilized substrate and position the microneedle tip within the droplet to evaluate the effectiveness of the capillary channel; however, such requires an additional component and additional steps with a very high risk of contamination of the control solution if the substrate is not adequately sterilized.
Even if a sterile substrate can be ensured for such prior art techniques, there is no means to truly mimic operating conditions wherein the needle is dispensed in a manner to penetrate the skin surface and wick accessed fluid there beneath. More specifically, factors like the ability of the needle to penetrate skin at the speed, angle, and depth as occurs under actual operating conditions, the tip strength of the needle, and the ability of the needle to provide suitable capillary action to fluid from within a solid medium, are unable to be evaluated.
As such, there is a need for improved techniques and systems for containing and dispensing control solutions and other reagents and agents for single-dose usage.